Okay... Day one examination completed yesterday, and now my observations...
First of all, the comparisons to other helmets, positive and negative... Well... Numbers always help. A lot of things can look either really similar or really dissimilar, absent context, so I decided to tackle some of the key points.
First thing I noticed was that the rear traps were positioned closer together than the ones on either my MR CE or my TE2. Matching HBS to MR CE crown base to crown base, the HBS is noticeably smaller. Out came the measuring things. Measuing around at the top of the brow trim (where the HBS crown ends, since the brow trim is part of the faceplate), the TE2 is 754mm around, the MR CE is 760, and the HBS is 751. So, closer to the original than to the MR CE, or than the MR CE is to the original, but still missed the mark. Since oth were purportedly laser-scanned off originals, one wonders if the dimensions were tweaked to prove provenance of any potential recasts...
Then I addressed myself to the faceplate. Interestingly, the tweaked crown dimensions don't really carry over to the rest of the helmet. Across the eyes, from outer corner across the bridge to outer corner, is 235mm on my TE2, 237 on the MR CE, and 230 on the HBS. But, as has been observed by others, the outer corners of the eyes are rounded off a lot compared to the originals. Corrected to more of a point, that can be made to match the wider measurements. The lens height, at widest point, is 32 and 29mm on the TE2 (that vaunted asymmetry some hold so dear), 33mm on the MR CE, and 30 on the HBS... So whatever "squintiness" I felt I saw was in my head. With a little bit of filing, my bubble lenses will fit like a dream.
The frown width, bearing in mind I'd already modded the frown on my MR CE to be properly Stunt-y, is right about 210mm on all three.
The side tube "real estate" (how much distance there is to work with), as measured along the bend from cheek to side tube, from the aerator shroud back... The originals vary a lot, and can be trimmed from way long to whatever overlap for a given helmet. Students of the original props know how all over the place this can be. So, confining myself to the more locked-in measurements... The MR CE has about 102mm before it ends at the earcap strap, and the HBS has about 122mm.
Lastly, the earcaps themselves... Apart from the greeblies and their orientation, the HBS is pretty much dead-on size-wise to the TE2 -- 65mm across the base, and roughly 60mm across the cap part itself. Meanwhile, the tiny MR CE earcap base is 58mm across. But I'd already been planning to address that. At this point, I may snag a regular helmet (which are all over my local TRU, Target, and WalMart) just to cannibalize the earcaps for my MR CE rework.
All the other gross measurements line up pretty well -- height of helmet back, overall width,etc. The undercut is as egregiously abbreviated as the MR CE, and that can be the reason for why it looks like it has such a pronounced angle from aerator shroud to side tube in profile. Extending the undercut in the right places will soften that angle to better resemble the original.
A few pics to illustrate what I mean:
--Jonah